Despite ongoing construction, the 1,070-foot-tall Salesforce tower at 415 Mission St. officially opened its doors on Monday, and so far, one tenant has initiated the move inside.

That occupant is none other than Salesforce, the tower’s anchor tenant and namesake.

In a bid to expand its San Francisco headquarters, Salesforce initially signed a lease with developers Boston Properties and Hines in 2014 for 714,000 square feet, or 32 floors — snagging the 61st floor on top — inside of the South of Market office building formerly known as the Transbay Tower.

It has since expanded its lease and will eventually occupy 36 floors throughout the tower.

The spaces are going fast. A total of 1.4 million square feet of leasing space was available inside of the building, and according to Helen Han, marketing director for Boston Properties, 97 percent of it has been leased out.

“We have one floor left,” she said.

Construction to the tower began in 2013, which rose amid criticism to be The City’s tallest building.

On Friday, light construction continued inside of the massive skyscraper. “We are still working on the buildout of individual tenants space,” Han said. “It’s touch-ups.”

That didn’t deter Salesforce from opening for business earlier this week. On Monday, CEO Marc Benioff posted a photo of the tower’s “first occupants” to Twitter, calling the moment “very historic.”

According to Han, the Salesforce employees had occupied two of the tower’s 61 floors by Friday, and are “coming into the building in stages.”

Over 600 Salesforce employees will occupy the tower by the end of January, according to Benny Ebert-Zavos, real estate communications specialist at Salesforce.

While Salesforce is currently the only tenant inside of the tower, others, including co-working space operator Wework, have signed leases, and are expected to move in gradually.

While still under construction, the tower’s top floor is leased by Salesforce and dubbed “Ohana,” or family in Hawaiian, a reference to Salesforce’s culture and real estate design concept of open views, sustainable materials and areas dedicated to wellness and mindfulness on dedicated floors.

That floor will serve as a lounge and event space, to be made available to nonprofit organizations for free during the weekdays.

Interest in the “Ohana Floor” has been “incredible,” according to Ebert-Zavos. “The community is a key stakeholder in our success and we’re proud to offer a world-class space to nonprofits and NGOs who are changing the world,” he said.

The company announced on Thursday that by the end of the year, the tower will feature the largest on-site water recycling system in a commercial high-rise building in the U.S.

Wastewater from showers, sinks, toilets, urinals and rooftop rainwater collection sources will be treated within the tower and recirculated through a separate pipe system throughout the building, according to a statement from Salesforce.

The system will reduce the building’s drinkable water consumption by 76 percent, saving up to 30,000 gallons of fresh water a day, equivalent to the yearly water consumption of 16,000 San Francisco residents, according to Ebert-Zavos.

Also in the tower’s future is the “highest public art display in the country,” according to Han. Boston Properties has worked with San Francisco based-LED artist Jim Campbell on a light display for the top of the tower.

The display is likely to be unveiled — and the tower’s crown illuminated — by late spring, Han said.